In many fluid flow applications, it is often necessary that the flow from an upstream source be cleaned or strained before use in downstream components. In this regard, strainers are used to protect such downstream equipment by mechanically removing solids from flowing fluids via a straining element, such as a perforated, mesh, or wedge-wire straining element. Although many designs and configurations of strainers exist, duplex strainers provide an added advantage over other straining systems by permitting continuous straining and cleaning of a flow. Specifically, duplex strainers generally include two strainer chambers and some type of mechanism for diverting the flow from one chamber to the other to isolate the flow to a single chamber. This arrangement permits cleaning, servicing, or repairing of one chamber while the other one is in use, thereby enabling the flow through the duplex strainer to remain substantially continuous.
A number of different designs for duplex strainers have been used, with varying valve designs (e.g., scotch yokes, ball valves) for switching the flow between strainers, but each design both has advantages over other options and suffers from one or more problems, such as number and complexity of components, space requirements, effectiveness in flow isolation, and/or ease of operation. Accordingly, an improved duplex strainer is desirable, for example one with a design to effectively control the flow between and among multiple strainer assemblies while minimizing the problems found in prior art designs.